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HugeBackupActivity.javaAPI DocAndroid 5.1 API8144Thu Mar 12 22:22:44 GMT 2015com.android.hugebackup

HugeBackupActivity

public class HugeBackupActivity extends android.app.Activity
Deliberately back up waaaaaaay too much data. Cloned with some alterations from the Backup/Restore sample application.

Fields Summary
static final String
TAG
static final Object[]
sDataLock
We serialize access to our persistent data through a global static object. This ensures that in the unlikely event of the our backup/restore agent running to perform a backup while our UI is updating the file, the agent will not accidentally read partially-written data.

Curious but true: a zero-length array is slightly lighter-weight than merely allocating an Object, and can still be synchronized on.

static final String
DATA_FILE_NAME
Also supply a global standard file name for everyone to use
android.widget.RadioGroup
mFillingGroup
The various bits of UI that the user can manipulate
android.widget.CheckBox
mAddMayoCheckbox
android.widget.CheckBox
mAddTomatoCheckbox
File
mDataFile
Cache a reference to our persistent data file
android.app.backup.BackupManager
mBackupManager
Also cache a reference to the Backup Manager
Constructors Summary
Methods Summary
public voidonCreate(android.os.Bundle savedInstanceState)
Set up the activity and populate its UI from the persistent data.


                 
    
        
        super.onCreate(savedInstanceState);

        /** Establish the activity's UI */
        setContentView(R.layout.backup_restore);

        /** Once the UI has been inflated, cache the controls for later */
        mFillingGroup = (RadioGroup) findViewById(R.id.filling_group);
        mAddMayoCheckbox = (CheckBox) findViewById(R.id.mayo);
        mAddTomatoCheckbox = (CheckBox) findViewById(R.id.tomato);

        /** Set up our file bookkeeping */
        mDataFile = new File(getFilesDir(), HugeBackupActivity.DATA_FILE_NAME);

        /** It is handy to keep a BackupManager cached */
        mBackupManager = new BackupManager(this);

        /**
         * Finally, build the UI from the persistent store
         */
        populateUI();
public voidonRestoreButtonClick(android.view.View v)
Click handler, designated in the layout, that runs a restore of the app's most recent data when the button is pressed.

        Log.v(TAG, "Requesting restore of our most recent data");
        mBackupManager.requestRestore(
                new RestoreObserver() {
                    public void restoreFinished(int error) {
                        /** Done with the restore!  Now draw the new state of our data */
                        Log.v(TAG, "Restore finished, error = " + error);
                        populateUI();
                    }
                }
        );
voidpopulateUI()
Configure the UI based on our persistent data, creating the data file and establishing defaults if necessary.

        RandomAccessFile file;

        // Default values in case there's no data file yet
        int whichFilling = R.id.pastrami;
        boolean addMayo = false;
        boolean addTomato = false;

        /** Hold the data-access lock around access to the file */
        synchronized (HugeBackupActivity.sDataLock) {
            boolean exists = mDataFile.exists();
            try {
                file = new RandomAccessFile(mDataFile, "rw");
                if (exists) {
                    Log.v(TAG, "datafile exists");
                    whichFilling = file.readInt();
                    addMayo = file.readBoolean();
                    addTomato = file.readBoolean();
                    Log.v(TAG, "  mayo=" + addMayo
                            + " tomato=" + addTomato
                            + " filling=" + whichFilling);
                } else {
                    // The default values were configured above: write them
                    // to the newly-created file.
                    Log.v(TAG, "creating default datafile");
                    writeDataToFileLocked(file,
                            addMayo, addTomato, whichFilling);

                    // We also need to perform an initial backup; ask for one
                    mBackupManager.dataChanged();
                }
            } catch (IOException ioe) {
            }
        }

        /** Now that we've processed the file, build the UI outside the lock */
        mFillingGroup.check(whichFilling);
        mAddMayoCheckbox.setChecked(addMayo);
        mAddTomatoCheckbox.setChecked(addTomato);

        /**
         * We also want to record the new state when the user makes changes,
         * so install simple observers that do this
         */
        mFillingGroup.setOnCheckedChangeListener(
                new RadioGroup.OnCheckedChangeListener() {
                    public void onCheckedChanged(RadioGroup group,
                            int checkedId) {
                        // As with the checkbox listeners, rewrite the
                        // entire state file
                        Log.v(TAG, "New radio item selected: " + checkedId);
                        recordNewUIState();
                    }
                });

        CompoundButton.OnCheckedChangeListener checkListener
                = new CompoundButton.OnCheckedChangeListener() {
            public void onCheckedChanged(CompoundButton buttonView,
                    boolean isChecked) {
                // Whichever one is altered, we rewrite the entire UI state
                Log.v(TAG, "Checkbox toggled: " + buttonView);
                recordNewUIState();
            }
        };
        mAddMayoCheckbox.setOnCheckedChangeListener(checkListener);
        mAddTomatoCheckbox.setOnCheckedChangeListener(checkListener);
voidrecordNewUIState()
Another helper; this one reads the current UI state and writes that to the persistent store, then tells the backup manager that we need a backup.

        boolean addMayo = mAddMayoCheckbox.isChecked();
        boolean addTomato = mAddTomatoCheckbox.isChecked();
        int whichFilling = mFillingGroup.getCheckedRadioButtonId();
        try {
            synchronized (HugeBackupActivity.sDataLock) {
                RandomAccessFile file = new RandomAccessFile(mDataFile, "rw");
                writeDataToFileLocked(file, addMayo, addTomato, whichFilling);
            }
        } catch (IOException e) {
            Log.e(TAG, "Unable to record new UI state");
        }

        mBackupManager.dataChanged();
voidwriteDataToFileLocked(java.io.RandomAccessFile file, boolean addMayo, boolean addTomato, int whichFilling)
Handy helper routine to write the UI data to a file.

            file.setLength(0L);
            file.writeInt(whichFilling);
            file.writeBoolean(addMayo);
            file.writeBoolean(addTomato);
            Log.v(TAG, "NEW STATE: mayo=" + addMayo
                    + " tomato=" + addTomato
                    + " filling=" + whichFilling);